missing links (e.g. create content) in admin_menu

I started to experience this problem, when I updated to the second newest XAMPP (1.7.2). All newly installed Administration menus were missing links. Now I saw, that there is a newer XAMPP, but the problem still arises.

On the left, where the favicon is, there is no more links, when the mouse hovers it. (Missing links: Flush all caches, Run cron, Run updates, Disable developter modules, Drupal.org)
"Content management" is missing: Create content (this is, where I first noticed the problem, see attached screenshots)
"Site configuration" is missing: By module
Maybe there are more links missing, but I did not look for them.

Just to make sure, that no other module got in the way, I installed a fresh drupal 6.15 with only admin_menu 6.x-1.5. I also tried different themes. => problem as described above.

Sometimes there was a problem with admin_menu_admin_menu mentioned, and something about the parameter expected.

warning: Parameter 1 to admin_menu_admin_menu() expected to be a reference, value given in C:\xampp\htdocs\dump\drupal-6.15\includes\module.inc on line 483.

So I looked for the function and found out, that if I changed applied following workaround and "Wipe and Rebuild" the admin_menu, that all the missing Links are back.

Does anyone know why this is?
Is there any known problem in using this workaround?

Workaround:
admin_menu.inc change line 107:
function admin_menu_admin_menu(&$deleted) {
into:
function admin_menu_admin_menu($deleted) {

Environment:
Windows 7 Ultimate 64bit
Firefox 3.5.6
Opera 10.10

###### Apache Friends XAMPP (Basis Package) version 1.7.3 ######

+ Apache 2.2.14 (IPV6 enabled)
+ MySQL 5.1.41 (Community Server) with PBXT engine 1.0.09-rc
+ PHP 5.3.1 (PEAR, Mail_Mime, MDB2, Zend)
...